Disposable nonwoven substrates are employed for the production of a wide variety of consumer products which are generally used once and discarded. Such products include disposable cleansing wipes, disposable diapers, disposable adult incontinence products, disposable pads typically employed in hospitals for absorption of body fluids and cosmetic applicators or cosmetic pads for removal of make-up and other materials from a keratinous substrate.
Such commercial products constitute an industry having ever increasing growth potential and expansion of utility. However, as virtually all such products potentially enter the environment through landfill or sewage systems, there is a need for a disposable nonwoven material that is simple to produce, contains a minimal or no amount of chemical components that have poor biodegradeability such as binders, adhesives or thermoplastic polymers and yet has good wet tensile strength as required for performance. In addition, a product is sought which is constructed to have minimal lint content and meets codes for categorizing as a flushable article acceptable for municipal and private sewage systems, while being economical to produce.
Conventionally, nonwoven disposable wipe products can be produced via one of two basic technologies known in the industry as “airlace” and “hydraspun” processes. Different producers may conduct these technologies with variation based on intended end use and available production equipment but the basic principles of operation are retained.
Airlace methods combine the operations of depositing an airlaid web of staple length fibers and wood pulp fibers onto a nonwoven carrier layer or precursor base nonwoven web and hydroentangling the airlaid layer with the nonwoven carrier. This technology is described in U.S. Pat. No. 8,250,719 to Ouellette and the references described therein. In addition to employing a carrier web, Ouellette describes bonding the airlaid fibers with hot air or a spray adhesive.
According to the “hydraspun” method as described in U.S. Pat. No. 4,755,421 to Manning et al. a wetlaid web of pulp and manmade fibers is hydroentangled and dried. However, U.S. Pat. No. 5,292,581 to Viazmensky et al. indicates that such products suffer from poor wet strength and describe that the addition of binders substantially improves the strength. More recently, U.S. Pat. No. 7,732,357 to Annis et al. describes the use of binder fibers to the nonwoven sheet that upon heating become activated by at least partial melting and form fiber to fiber bonds. The binder fibers contain polyethylene, polypropylene, polyethylene terephthalate and mixtures thereof.
Therefore, there remains a need for a method to prepare a nonwoven web that contains no adhesive, binder or binder fibers, is convenient and economical to conduct and provides a dispersible nonwoven web having good performance strength, yet being acceptable as a flushable product for municipal sewer and private septic systems.